// 重写选择代码，支持多选
Q.SelectionInteraction.prototype.onstart = function(evt, graph) {
	if (evt.responded) {
		return;
	}
	//if(!isTouchSupport && isIE){
	//    graph.focus(true);
	//}
	var data = evt.getData();
	if (data && !graph.isSelectable(data)) {
		data = null;
	}
	if (data && Q.isMetaKey(evt)) {
		graph.reverseSelect(data);

		var event = new Q.InteractionEvent(graph, Q.InteractionEvent.SELECT, evt, graph.selectionModel);
		graph.onInteractionEvent(event);
		return;
	}
	if (data && graph.selectionModel.isSelected(data)) {
		return;
	}
	if (data) {
		graph.setSelection(data);
		graph.sendToTop(data);
	} else {
		// 注释掉，让节点能多选
		//      graph.setSelection(null);
	}

	var event = new Q.InteractionEvent(graph, Q.InteractionEvent.SELECT, evt, graph.selectionModel);
	graph.onInteractionEvent(event);
};

